Anionic F Doping-Induced Engineering of P2-Type Layered Cathode Materials for High-Performance Potassium-Ion Batteries

Abstract

P2-type layered oxides emerge as promising cathode candidate materials for potassium ion batteries. Nevertheless, unsatisfying cyclic stability hinders its practical application, chiefly arising from the deleterious phase transition and the Jahn-Teller distortion of Mn3+. Herein, an anion-doped strategy by incorporating F- into the P2-K0.6Zn0.1Ti0.05Al0.05Mn0.8O2 (KTMO) cathode materials is proposed. Raman testing was employed to investigate the material’s local chemical environment. The results denoted a slight shift to higher wavenumbers in the Eg and A1g peaks, which was ascribed to the shortening of the average TM-O bond length triggered by the addition of F. Ex-situ XRD analysis revealed that the material K0.6Zn0.1Ti0.05Al0.05Mn0.8O1.93F0.07 effectively suppresses the undesirable phase transformation. Moreover, the maximum variation in the lattice parameter c is only 2.2% during potassium insertion/extraction, which fully demonstrates the outstanding performance of this material in terms of structural stability. The strategy brings about excellent cyclic stability with a reversible capacity of 131.8 mAh g-1 and capacity retention of 76.8% after 100 cycles at 4.0 V. Therse findings offer novel insights for the design of cathode materials possessing optimal structures and enhanced performance in potassium-ion batteries.